Nematodes parasitize ~25% of the human population. Helminth targeting drugs, or anthelmintics, have been used to control parasitic nematodes for decades and many species are evolving multidrug resistance. In diverse organisms, multidrug resistance is mediated by increased expression and activity of enzymes that detoxify xenobiotics. Pharmacological compounds that target xenobiotic detoxification pathways would provide much needed tools for studying multidrug resistance and could greatly increase the useful life of current and future anthelmintics. Few pharmacological compounds are available for studying and targeting multidrug resistance and those that are available are not specific for nematodes and only target a single enzyme or class of enzymes. The transcription factor SKN-1 activates the expression of xenobiotic detoxification genes in the nematode Caenorhabditis elegans. Genetic inhibition of SKN-1 sensitizes C. elegans to diverse xenobiotics, and C. elegans can acquire resistance to anthelmintics by increasing the expression of genes that are regulated by SKN-1. SKN-1 is also essential for the development of embryos. Our recent studies have identified a principal pathway regulating SKN-1 that is highly divergent from pathways that regulate xenobiotic detoxification in mammals. Therefore, SKN-1 is a promising target for the development of drugs that disrupt embryonic development, decrease stress resistance, and inhibit xenobiotic detoxification in nematodes without affecting analogous pathways in humans. The small size, simple culturing characteristics, and genetic tractability of C. elegans makes it an ideal system to screen for inhibitors of xenobiotic detoxification genes. The first goal of this project is to develop and optimize a fluorescence-based assay of SKN-1 activity in C. elegans. The second goal of this project is to develop four secondary and counter screens to rapidly prioritize hit compounds and to test the assay in a pilot screen of 2000 compounds. After completion of these goals, a detailed description of the optimized assay will be submitted for entry into the Molecular Libraries Probe Production Centers Network (MLPCN).